Electrical Resistance
How resistance opposes current, what determines it in a conductor, how it changes with temperature, and how resistors combine in series and parallel.
Questions people ask
What is the difference between resistance and impedance?
Resistance applies to DC and to the purely resistive part of an AC circuit. Impedance covers AC generally, adding the frequency-dependent effects of capacitance and inductance.
Do resistors have polarity?
No. A resistor behaves identically whichever way round it is fitted, unlike diodes, electrolytic capacitors and most semiconductors.
Why is copper used for wiring rather than silver?
Silver conducts slightly better, but copper is roughly a hundredth of the price and easy to draw into wire. The tiny gain in conductivity is not worth the cost.
Does this page work offline?
Yes, after the first visit. The service worker caches it, so the reference stays available with no connection.
Last updated 22 August 2026